1. Field of the Invention
This invention relates generally to turbines and compressors having inner and outer casings which encompass the rotors and that are divided along a horizontal plane into upper and lower semi-cylindrical halves, and more particularly to an improved method and apparatus for "rolling out" the lower half of the outer casing without the necessity for removing the rotor.
2. Statement of the Prior Art
Axial flow turbines and compressors are typically provided with an inner casing that contains the rows of stationary nozzles for directing the motive fluid past the rotor blading. Such conventional inner casings are disposed within an outer casing structure for many well known reasons.
Since turbines and compressors must, from time-to-time, be disassembled for servicing and/or repairs, the inner and outer casings are divided into upper and lower halves that are removably joined to each other by bolts at suitable horizontal flanges. In a similar manner, the nozzle rows are also divided into upper and lower semi-circular halves so that they may be removed with the associated inner casing half as a unit, and then subsequently removed from the casing for repair or replacement.
Although the upper half of the inner casing is readily accessible for removal by first removing the upper half of the outer casing, the lower half of the inner casing has not been so easily removable. This problem is primarily due to the rotor's being supported in the lower half of the outer casing which interferes with such removal. It would, therefore, be desirable to provide methods and apparatus which facilitate repairs to or replacement of turbines and compressors having inner and outer casings which encompass the rotors and that are divided along a horizontal plane into upper and lower semi-cylindrical halves.
One known means which facilitates such repairs and replacement is disclosed and claimed in U.S. Pat. No. 3,493,212--Scalzo et al., which is assigned to the assignee of the present invention, and is incorporated herein by reference. Scalzo et al. teach an arrangement which not only permits ready removal of the lower half of the inner casing, together with the lower halves of the stationary nozzle rows, but also permits the removal without any preliminary removal of the rotor.
The above arrangement is attained by providing a roller structure that is insertable into the lower half of the outer casing and extends into rollable supporting relation with the inner casing. In such a manner, the inner casing is permitted to be rolled about its central longitudinal axis to an uppermost position in which it is free of the rotor, at which time it may be readily lifted clear of the lower half of the outer casing for repairs or replacement. One problem with the roller structure that is shown and claimed in Scalzo et al. is that it requires a number of precision machined parts which unnecessarily complicate its manufacturing process and increase the cost therefor.